Personal communication devices are becoming more widely adopted by the public. Devices such as cellular phones, personal digital assistants, and laptop computers give users a variety of mobile communications and computer networking capabilities. In recent years, personal communication devices have implemented capabilities for supporting additional types of communications applications that allow for real-time or near real-time communication outside of traditional voice communication using a wide variety of multimedia formats, including text, voice, music, and video.
Push-To-Talk (PTT) is a real-time voice-based communication service that allows personal communication devices to operate as a “walkie talkie”. Push-to-talk may be implemented as a half-duplex channel that is shared by all of the participants of a push-to-talk session. For example, a PTT-enabled mobile terminal may send a page to a network server to request establishment of a push-to-talk session with a remote user in response to a dialed number. Once the push-to-talk session has been activated, either participant may send a floor request (a request to use the half-duplex channel) by pushing a button on their mobile terminal. The network server may indicate that the floor request has been granted by, for example, an audio tone. Once the user has been granted the floor, he may broadcast speech over the channel by talking while holding in the button. Release of the button may release the floor, so that the half-duplex channel may then be used by another participant to the call or remain idle. While the push-to-talk session is active, it provides the user and remote user(s) an instant talk capability for communicating with each other. The push-to-talk session may be established between two users (point-to-point) or between three or more users (group talk). Push-to-talk sessions may be implemented over both packet-switched and circuit switched networks.
Instant messaging is another type of communications service that enables users of personal communications devices to communicate in real time over the Internet using text-based messages. In a typical instant messaging application, for example, AOL Instant Messenger (IM), a user may prepare and transmit a text message for delivery to one or more other users, typically on a so-called “buddy list.” The user may receive messages from members of the buddy list in a similar manner. In instant messaging applications, it is known to provide appointment/status information from personal information manager (PIM) software to the instant messenger, which may pass this status information to identified buddies.